1. Field of the Invention
This invention relates to motion image recording apparatus and, more particularly, to a motion image recording apparatus applicable to a digital camera which records a plurality of frames of image data onto a recording medium according to a recording instruction.
The invention is also concerned with digital cameras and, more particularly, with a digital camera for taking a picture of a subject according to a picture taking instruction and recording a taken image signal onto a recording medium.
2. Description of the Prior Art
In the conventional digital cameras, when a motion image recording mode is selected, a picture-taking process and compression process of motion image data are commenced responsive to an operation of a shutter release button. The compressed motion image data thus produced is temporarily stored into an internal memory. If the shutter button is thereafter put off, the picture-taking and compression processes are suspended and the compressed motion image data stored in the internal memory is then recorded collectively onto a recording medium. Meanwhile, when a still picture recording mode is selected, a one-frame picture taking process and compressing process of taken still image data are performed responsive to a shutter button operation. The compressed still image data thus produced is recorded onto the recording medium through the internal memory.
In the prior arts, however, in the case that the motion image recording mode is selected, compressed motion image data has to be once stored in the internal memory before recorded to the recording medium. This leads to a problem that a continuously recording time period is dependent upon an internal memory capacity. Also, even where the still image recording mode is selected, the processes of picture taking, compression and recording are conducted in a serial order fashion. Another problem lies in the prior arts, i.e. the interval of shutter button operations, or picture-taking time interval, increases particularly when successive shots are carried out.
It is therefore a primary object of the present invention to provide a motion image recording apparatus which is capable of recording motion images for a long time, in a manner regardless of its memory capacity.
Another object of the invention is to provide a digital camera which can shorten the picture-taking time interval.
In accordance with the present invention, a motion image recording apparatus for recording a plurality of successive frames of image data onto a recording medium in response to a recording instruction, comprises: an image writer for cyclically writing the image data to an internal memory; an image reader for cyclically reading out of the internal memory the image data to be recorded to the recording medium; and a disabler for disabling the image writer when an image write position and an image read position are in a predetermined relationship.
When a plurality of frames of successive image data are recorded onto a recording medium in response to a recording instruction, the image data is first written to the internal memory in a cyclical fashion. The image data written on the internal memory is read out by the image reader in a cyclical fashion and written to the recording medium. Accordingly, where the internal memory is small in capacity, a long time of motion images can be recorded to the recording medium. However, when an image write position and an image read position are in a predetermined relationship, the image writer is disabled by the disabler. As a result, there is no possibility that the unread image data be overwritten by the succeeding image data.
In one aspect of the invention, the internal memory has a plurality of image blocks, and each of the image block having a corresponding capacity to a predetermined number of frames of image data.
In one embodiment of the invention, the image writer preferably includes a selector and a image data writer. The selector cyclically selects the image blocks one by one, and an image data writer writes the predetermined number of frames of image data to a selected one of the image blocks by the selector.
In another embodiment of the invention, a plurality of block flags respectively correspond to the plurality of image blocks. A setter sets corresponding one of the block flags to the image block to which writing of the predetermined number of frames of image data has been completed. A resetter resets corresponding one of the block flags to the image block from which reading out of the predetermined number of frames of image data has been completed.
Here, the image reader includes an image data reader to read the image data by predetermined bytes at one time out of one of the image blocks, and a renewer to renew a read address each time reading out by the predetermined bytes has been completed; and the resetter including a detector to detect the read address, a determiner to determine a completion of reading out of the image block based on a result of detection by the detector, and a flag resetter to reset the block flag depending upon a result of determination by the determiner.
Also, the disabler disables the image writer depending upon a state of the block flag.
In another aspect of the invention, a compressor compresses the plurality of frames of image data. In this case, the image writer writes compressed image data having been compressed by the compressor to the internal memory, and the image reader reading the compressed image data out of the internal memory.
In still another aspect of the invention, a picture taking circuit takes a picture of a subject and produce the plurality of frames of image data.
In yet another aspect of the invention, a sound writer cyclically writes sound data related to the image data into the internal memory. Thereafter, a sound reader cyclically reads from the internal memory the sound data to be recorded onto the recording medium.
In accordance with the present invention, a digital camera, comprises: an input key for inputting a shooting instruction; an image sensor for shooting a subject; and a multitask CPU for concurrently performing, based on the shooting instruction, a write process to write a corresponding still image signal to the subject into an internal memory and a recording process to record the still image signal stored in the internal memory onto the recording medium.
A shooting instruction is inputted by the input key, and a subject is shot by the image sensor. When a shooting instruction is inputted, the multitask CPU performs concurrently a process of writing a still image signal obtained based on the shooting instruction into the internal memory, and a process of recording the still image signal written on the internal memory to the recording medium. This reduces the time interval of taking pictures particularly when conducting successive shots.
In one aspect of the invention, the write process includes a first determining process, an image write process and a preparation process. Here, the first determining process is to determine a presence or absence of the shooting instruction. The image write process is to write the still image signal into the internal memory when determined as a presence of the shooting instruction. The preparation process is to prepare an administration table for administrating address information of the still image signal stored in the internal memory. On the other hand, the recording process including an image read process and an image recording process. The image recording process is to read the still image signal out of the internal memory based on the administration table, while an image recording process is to record the still image signal read out by the image read process onto the recording medium.
In one embodiment of the invention, the write process further includes an estimation process and a first disable process. The estimation process is to estimate based on the administration table a signal amount of the still image signal written in the internal memory but not yet recorded. The first disable process is to disable the first determination process for a predetermined time period depending upon a result of estimation by the estimation process.
The estimation process preferably includes a first comparison process to compare the signal amount with a first predetermined value, and a second comparison process to compare the signal amount with a second predetermined value greater than the first predetermined value. The first disable process preferably includes a first suspension process to suspend the first determination process until a predetermined timing signal has been generated when the signal amount exceeds the first predetermined value, and a second suspension process to suspend the first determination process until the recording process has been ended when the signal amount exceeds the second predetermined value.
In another embodiment of the invention, the input key is a key to input the shooting instruction and a shooting preparation instruction, and the shooting preparation instruction being to be inputted when the input key is shifted to a first operation state, and the shooting instruction being to be inputted when the input key is shifted to a second operation state through the first state.
Here, the write process preferably includes a second determination process, a shooting preparation process and a second disable process. The second determination process is to determine a presence or absence of the shooting preparation instruction. The shooting preparation process is to prepare for shooting the subject when determined as a presence of the shooting preparation instruction. The second disable process is to disable the second determination process depending upon a time difference between a determination in a last time of a presence of the shooting instruction and a determination in a present time of a presence of the shooting instruction.
The shooting preparation process preferably includes an adjustment process on a shooting condition and a detection process to detect a successive shotable number.